9^ PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [DeC. S> 



The strata at Brook Point continue for several hundred yards 

 along the cliffs, and it was in these beds that the author discovered 

 the large mussel-shells that inhabited the river of the country already 

 alluded to. The Unio valdensis (as this species has been named) was 

 first observed in the sandy clay beds immediately above the fossil fo- 

 rest, and several examples have since been found in other places along 

 this line of cliffs. It is a species remarkable both for its large size and 

 for the perfect state of preservation in which it is found. The horny 

 ligament generally remains in a carbonized state, and the body of 

 the animal occurs as molluskite, but the substance of the shell is 

 often changed into compact calcareous spar, and nodules of crystal- 

 lized sulphate of barytes of a pink colour are not uncommon within 

 the shells *. From the same strata bones of the Iguanodon and other 

 Wealden reptiles are obtained, the specimens usually collected 

 having been washed out of the cliffs by the inroads of the sea, and 

 being strewn along the shore. In this way they have commonly 

 suffered so much by attrition that the processes are destroyed, and 

 those parts defaced which are of most value to the anatomist as 

 distinctive characters. 



The number of bones collected along this coast during the last 

 ten years amounts to many hundreds, and although from their rolled 

 condition most of them are of no value as specimens, yet they serve 

 at least to show the abundance of these relics. Many of them sur- 

 pass in magnitude the largest of the Wealden bones in the British 

 Museum. 



The strata at Sandown Bay, shown in Dr. Fitton's section, emerge 

 from under the greensands, and consist of clay, clay-shale, sand, and 

 slabs of bluish-gray argillaceous limestone abounding in the usual 

 shells of these freshwater deposits ; and here, as at Brook, the bones 

 of colossal reptiles are continually washed out of the cliffs. This 

 shelly limestone, occurring in layers from one to three inches thick, 

 and of uniform surface, is often employed for paving ; slabs with 

 the shells of the Cyclas^ Paludina and Unio may often be detected 

 in the pavements at Ryde and other places in the island, as at Bat- 

 tle, Hurstraonceaux and elsewhere in Sussex. The surface of the 

 slabs is often deeply sculptured with ripple-marks ; and very recently 

 some markings have been observed that are supposed to be the im- 

 prints of the feet either of birds or reptiles. 



Fossil remains of many of the large reptilian animals which have 

 conferred so much celebrity on the strata of Tilgate Forest have 

 been obtained from these contemporaneous deposits in the Isle of 

 Wight, and amongst them the bones of the Megalosaurus^ StreptO' 



lignite, sulphuret of iron, and shelly limestone. The lignite he thinks might have 

 suppUed the carbonic acid, and he quotes the authority of Dr. Liebig in favour of 

 this view. 



* Doubt having been expressed as to the correctness of assigning a new spe- 

 cific name to this shell, the author states that Mr. James Sowerby, who figured 

 and described the Unio Martini of Dr. Fitton (presumed by some to be the same 

 species), concurs in his opinion, and has figured the shell under the abovename 

 for the ' Mineral Conchology.' 



